2005 ICRP Recommendation

Draft document: 2005 ICRP Recommendation
Submitted by Lynne Fairobent, American Association of Physicists in Medicine
Commenting on behalf of the organisation

December 23, 2004 International Commission on Radiological Protection SE-171 16 Stockholm Sweden Dear Members of the Commission: The American Association of Physicists in Medicine is pleased to be able to comment on the ¡§the next Fundamental ICRP Recommendations.¡¨ The AAPM is concerned that many of the recommendations in the report will have a negative effect on the availability of quality health care because they will reduce accesses to that care. The AAPM feels that the commission should seriously rethink many of these recommendations that appear to lack a firm grounding in scientific knowledge. Attached are specific comments on the recommendations. The American Association of Physicists in Medicine (AAPM), which represents more than 5,000 medical physicists throughout the United States and other countries, is a Member of the American Institute of Physics. The AAPM promotes the application of physics to medicine and biology and encourages interest and training in medical physics and related fields. Yours truly, G. Donald Frey, Ph.D. President Attachment: AAPM detailed comments Attahcment The American Association of Physicists in Medicine (AAPM), which represents more than 5,000 medical physicists throughout the United States and other countries, is a Member of the American Institute of Physics. The AAPM promotes the application of physics to medicine and biology and encourages interest and training in medical physics and related fields. General Comments: 1. Availability of the Foundation Documents. Although the AAPM is pleased to offer comment on the proposed recommendations, it is with reservation since the five ¡§foundation documents¡¨ still are not available for public comment. AAPM urges the ICRP to consider delaying the publication of the final recommendations until the foundation documents have been presented for public review and comment. 2. Concept of Dose Constraint. As presented the ¡§concept of dose constraint¡¨ needs further discussion and justification. As defined in the current draft, the term ¡§constraint¡¨ appears to have multiple meanings, some of which overlap with the meaning of the U.S. term ¡§limit¡¨. Specifically, clarification is needed on the use of the term ¡§failure¡¨ to indicate not meeting a constraint. This may or may not be interpreted in the U.S. to mean that a legal or regulatory limit has been exceeded. 3. Problem with the implementation of dose constraint vs. dose limits. The concept of dose constraint certainly is not new. It was introduced in ICRP 60 and it is used by many regulatory agencies throughout the world to optimize radiation protection. One of the objectives of the new Recommendations is to emphasize the role of dose constraints and diminish the role of dose limits. The introduction of the maximum dose constraint, however, makes the distinction between the two parameters terribly confusing; especially in the Summary at the beginning of the document (Table S1 cannot be comprehended as is). Regulators will not know how to implement dose constraints and will tend to adopt dose constraints as limits for the sake of simplicity. In fact, this has already happened in many developing countries, where regulating constraints and limits as separate entities would create a burden beyond the capabilities of the regulatory infrastructure in place. The whole section on dose constraints needs to be rewritten and clear advice on how they are to be implemented, given. In particular, it is essential to re-write paragraph (132) and (S4): ¡§¡Krestrictions on individual dose from specified sources in all situations within their scope¡K should be applied to the exposure of actual or representative individuals. They provide a level of protection for individuals that should be considered as obligatory and not maintaining these levels of protection should be regarded as a failure.¡¨ Other confusing paragraph is (145). 4. For medical physicists, paragraph (164) is bothersome. It suggests using 0.3 mSv as a dose constraint for the public: ¡§in case of multiple dominant sources a figure of 0.3 mSv/year would be appropriate¡¨. How is the regulator to know about multiple dominant sources? The rewrite of the NCRP 49 Report encountered the problem of whether to use 1 mSv or 0.25 mSv for public protection limits in shielding design of diagnostic radiology facilities. After months of struggle, the NCRP published Statement No. 10, which clarified: ¡§After a review of the application of the guidance in NCRP (1993) to medical radiation facilities, NCRP has concluded that a suitable source control for shielding individuals in uncontrolled areas in or near medical radiation facilities is an effective dose of 1 mSv in any year. " Yet, many countries (the UK for instance) have adopted 0.3 mSv as a shielding constraint. If the new ICRP keeps this figure in this paragraph, many more countries will adopt this value. Since the money available for health care is limited, radiological equipment maintenance and/or replacement as well as staff training are sacrificed in order to comply with regulatory requirements for shielding. The net result is a significant detriment to patient management, especially in developing countries. The problem may lie in the definition of single source (174). How can ¡§the x-ray equipment in a hospital¡¨ be a single source? What are we going to do for shielding calculations? Take the ¡§geometrical center of all the x-ray units as an ¡§effective point source¡¨ or the edge of the closest one to the point of measurement? 5. Radiobiological basis uncertainties. The text and especially Annex A summarize current radiobiological experimental and epidemiological studies carried out since ICRP 60. Some of the findings do not support current ICRP views. For medical physicists, an example is the wR value for low energy x-rays like those used in mammography. Because of the effect of Auger electrons, wR may be greater than 1. Instead, the Commission has chosen to increase the value of wT, declaring the breast tissue more radiosensitive than it was before. There are many other examples of such cases, where in analyzing the results of recent studies, the Commission concludes that the uncertainty associated to the findings is such that, in their judgment, changes are not warranted. If this is the case, why not wait a few more years to change the Recommendations, when the studies have been replicated and the data are more reliable? 6. Averaging and weighting. When data are unreliable (uncertainties are high), the effect of averaging compounds the problem. The Commission acknowledges that cancer incidence is population, gender and age dependent. Furthermore, it is tissue specific. Yet, it chooses to average across all the categories for the sake of ¡§simplicity¡¨. One wonders why go through the trouble of reviewing all the scientific literature if the results are not to be used in a scientific manner. Particularly troublesome is how arbitrary some decisions seem. (A7), (A9), (A14), (A17), (A24), (A28), (A29), (A31), (A36), (A39) are examples of how the Commission has arrived to ¡§ICRP judged values¡¨. 7. Justification of practices. In ICRP 60, justification of practices was a pillar of radiation protection (5). Now in paragraph (18), the Commission acknowledges that factors other than radiation protection enter into the decision of countries adopting practices involving radiation. This is not new. Still, the way the Commission rationalizes it (10) is not clear at all and it should be re-written. Radiation protection is just one factor for governments to take decisions on legalizing practices, and clearly, not the most important one. The change in emphasis would not be bad, if now [(19), (148), (213)], the Commission were not to insist that medical practices involving radiation need to be justified not only in a generic form [(216), (218)], but individually (219), especially in ¡§complex diagnostic procedures¡¨ (which are not defined) and radiation therapy. Regulatory authorities demanding justification of each patient undergoing interventional radiology or radiation therapy is an interference with a medical act and it should not be allowed. Interestingly, there are inconsistencies on this issue throughout the document. For example (222) states that: ¡§The medical procedures causing patient exposures are clearly justified¡¨. Are they or aren¡¦t they? Another example (not related to medical exposures) is (161), which seems to lead to the need of justification. Also (185), which refers to ¡§practices that are already justified in normal conditions¡¨. 8. Patient Protection Optimization and Diagnostic Reference Levels. The last sentence of paragraph (147) should be re-written for greater clarity, as nothing has been said before about the need to reduce dose, and the point the paragraph is trying to make is a very important one. (223) defines Diagnostic Reference Levels as dose levels against which ¡§unusually high doses¡¨ are to be compared. What happens if the doses are too low? The International Basic Safety Standards (IAEA 1996) in regards to Reference Levels (called ¡§Guidance Levels¡¨), also recommended that ¡§corrective actions be taken as necessary if doses or activities fall substantially below the guidance levels and the exposures do not provide useful diagnostic information and do not yield the expected medical benefit to patients¡¨. 9. Operators vs. Operating management. In the nuclear power community, operators are the managers of the facility. In the medical field, operators are the individuals who operate a machine such as an x-ray unit or a linear accelerator. To refer to facility managers, the document uses two terms ¡§operators¡¨ [(140), (190)] and ¡§operating management¡¨ [(156), (174)]. It is recommended that the latter term be used throughout to avoid confusions. 10. Definition of occupational exposure. The International Labor Organization (ILO) defines occupational exposure as that incurred in one¡¦s work, regardless of whether the workers are radiation workers or not. The document in (143) has a slightly stricter definition. Consideration should be given to making this definition consistent with that used in the International Basic Safety Standards and adopted the ILO definition. 11. Protection of the environment. This section is not fully developed in the current draft and should be excluded until the issue is scientifically more mature. Specific Comments: 1. Paragraph S(5): What is the difference between ¡§normal situation¡¨ and ¡§case of controllable existing exposure¡¨? Especially ¡§normal situation¡¨ is not defined in the Recommendations. The semicolon on line 6 should be exchanged by colon. 2. Paragraph (S6): ICRP 2005 draft: Page 2: (S6) This is because there is presumed to be some probability of health effects even at small increments of exposure to radiation above the natural background. ICRP 2005 draft: Page 16: For protection purposes, it is assumed that these effects increase with increasing radiation dose , with no threshold, and that any increment of exposure above the natural background produces a linear increment of risk. Comments on these two items: (a) These presumptions are contrary to the position statement of Health Physics Society, which states in part: "Below 5-10 rem (which includes occupational and environmental exposures), risks of health effects are either too small to be observed or are nonexistent." (See: http://www.hps.org/documents/radiationrisk.pdf) The worldwide natural background radiation is not a constant. It varies considerably from location to location, with no significant observed adverse health effects from being exposed to elevated natural background radiation levels. In fact several studies have reported the opposite: i.e. improved health with increased background radiation. Thus, the basic assumptions made above are without merit. 3. Paragraph S(17): The text ¡§The weighting factor for Remainder tissues is to be applied to (the) dose averaged over the 14 specified organs and tissues that consist the Remainder¡¨ would be misleading in the cases when only part, e.g. 5 organs are exposed and the dose in 9 of the Remainder is zero. In these exceptional cases I would propose to apply the procedure described in footnote ¡§b¡¨ on page 315 of IAEA¡¦s ¡§International Basic Safety Standards for Protection against Ionizing Radiation and for Safety of Radiation Sources¡¨ (IAEA, Safety Series No.115, Vienna 1996). 4. Paragraph (21): What is the difference between a ¡§normal situation¡¨ and a ¡§controllable situation¡§. A source in a normal situation has to be in a controllable situation, at least in the sense of paragraph (15). 5. Paragraph (19): The particularity of medical exposure is that justification has to be applied to the irradiation of each one patient based on the balance between the risk to cause a detriment and the risk that the patient will not be cured if the corresponding exposure is not be done. The solution of this dilemma relays on the degree of qualification of the medical practitioner who prescribes a medical exposure. Thus the government¡¦s problem is to introduce strict requirements to the qualification of those practitioners who are authorized to prescribe medical exposures. 6. Paragraph (40): The discussion on the dependency of RBE on LET is misleading in my opinion. The text implies that high-LET radiation has a higher RBE (¡§High LET radiation, from neutrons and alpha particles, causes more damage per unit of absorbed energy than low LET radiation.¡¨). This may be true for a very general view. However, for example, protons with the same LET than helium ions can have a higher RBE at a given dose (see for example Belli et al: Int J Radiat Biol. 1992 May; 61(5):625-9; ¡§Direct comparison of biological effectiveness of protons and alpha-particles of the same LET. II. Mutation induction at the HPRT locus in V79 cells.¡¨). This phenomenon is due to differences in track structure, i.e. differences in the yield and energy of ƒÔ-electrons. It should be pointed out that the fact that high LET radiation is more effective is only a rule of thumb and that LET is generally not a valuable parameter to characterize RBE since it does not take into account microscopic dose deposition. Even for a single radiation modality (e.g. alpha particles) the statement is only an approximation since the RBE increases with LET only up to a certain LET and then eventually decreases. At the end of the paragraph it says ¡§(see Section 3.6.)¡¨. There is no section 3.6. in the text. 7. Paragraph (39): For clarity it would be useful to complete this text with the mathematical formula, equation (2) in paragraph (52), or with reference to it. What is the reason to have omitted the quantities committed effective dose and collective effective dose? The sense of the latter is partially mentioned at the end of paragraph (17). 8. Paragraph (49): Re-word. Not all photons and neutrons are ¡§penetrating¡¨. 9. Paragraph (62): The term ¡§radiation quality¡¨ is not defined in these Recommendations and obviously is mentioned instead of the radiation¡¦s biological efficiency. 10. Paragraph (66): The quantity H* should be mentioned with its name. Its correct sign is H*(d) and a reference to ICRU-report 51 would be helpful for the reader, even to understand why it is mentioned in plural. 11. Paragraph (70): Paragraph (70) should be omitted as it is replaced by paragraph (71). 12. Paragraph (99): Table 5, Is 1% incidence a sufficient argument to set absorbed dose thresholds for nonstohastic biological effects? Is this incidence with excluded spontaneous incidence? 13. Figure 2: Figure 2 has the caption ¡§Radiology¡¨ under a photograph of a linear accelerator. It should say ¡§Radiation Oncology¡¨ or the photo should be changed to show a diagnostic or interventional x-ray unit, including a CT scanner. 14. (141) and (146): Medical exposure definition: (141) and (146) should be re-written for greater clarity. The exposure of the staff is occupational exposure, not medical exposure. 15. Paragraph (158): ICRP 2005 draft: Page 42: (158) The worldwide average annual effective dose from all natural sources, excluding radon, quoted in the UNSCEAR (2000) report is 1.2 mSv with a range of 0.8 to 2.4 mSv. This has been rounded by the Commission to 1 mSv/yr. A general scheme for the need for action and the level of dose, as a fraction or multiple of the average annual natural background, has been proposed by ICRP and is shown in Figure 3. 16. Paragraph (159): ¡§. . .doses of about 100 mSv are. . .¡¨ should be corrected to ¡§. . . dose of about 100 mSv in 1 year (better: accumulated in 365 consecutive days) are . . .¡¨ in order to be in line with the dose constraints in Table 7 of paragraph (165). 17. Paragraph (159): ICRP 2005 draft: Page 42: (159) The need for action is likely to be high if an effective dose from a single source is more than about a hundred times the global average background dose. Individual effective doses of about 100 mSv are therefore about the most that should be allowed for workers in any other than saving life or preventing serious injury, or preventing catastrophic circumstances. Why hundred? The factor of hundred times the global average is arbitrary and is unjustified. The limit should be set at a fraction (e.g., 1/3) of the smallest dose that has been shown to be harmful, in order to give a margin of safety. In the absence of any demonstrated adverse health effects at these low radiation levels, using the average value of 1 mSv/year as dose limit is not justified. Since people have lived in much higher background radiation levels in many parts of the world, and they have not shown increased incidence of cancer, the dose limit should be based on the highest background levels in which people have lived without increased incidence of cancer, e.g. 1/3 of the highest natural background levels without increased incidence of cancer, to give a safety margin. The present regulatory low dose limit for public has certainly led to tremendous waste of our resources without any measurable benefit. 18. Paragraph (165): Should be completed ¡§Additional restrictions are needed in the situation when one individual is exposed to several significant sources in order to meet the corresponding dose limits.¡¨ 19. Paragraph (175): Lowers the fetal dose limit by 5-fold. This constraint is a fraction of background and would have an absolutely negative impact on medical workers who have declared their pregnancy. Such an unjustified constraint would preclude women from working with radiation in a medical environment. 20. Paragraph (175): ¡§. . . under the system of protection recommended by the Commission . . .¡¨ to be exchanged by ¡§. . . under the system of protection of workers recommended by the Commission . . .¡¨ 21. Paragraph (175): Suggested change: ¡§. . .women who may be pregnant . . .¡¨ to be exchanged by ¡§. . . women who are pregnant . . .¡¨ , because a woman may be pregnant at almost any time; 22. Paragraph (213-216): The ICRP discussion on the justification of a medical practice as a source of exposure is warranted. However, the recommendation that the physician must provide justification for each individual medical radiation study is totally unacceptable. For an international body to set standards on the practice of medicine at an individual basis is bad. 23. Paragraph (231): Paragraph 231 is missing words. 24. Paragraph (247): ¡§Deterministic effects¡¨ should be replaced by ¡§tissue reactions¡¨ in (247). 25. Paragraph (A26) and (A27): H needs to be defined in the formulas of (A26) and (A27).